The demon might be the one pulling the strings, since this is alrdy noted as a spoiler this is a spoiler relating to the latest GC mission.

Upon completion it pretty much goes that they don't think the Emperor is pulling the strings so it must be someone else pulling the strings behind Legatus Nael van Darnus or it could even be him taking the form of Legatus Nael van Darnus.

Looking at the helmet I can't help but feel that there is a bit of a similarity of their shape



But ya, good catch I completely forgot about this CS, should really take the time to look through the Main scenario lol. It is possible that he'll have a connection to the main plot and most likely with the battle we're suppose to be having come 1.23 we'll find out who's the one that's manipulating Nael to "purify" Eorzea.